The insulation device must also, in certain cases, fulfill another function, a priori antagonistic to that presented above, and which is to attenuate dynamic loads, such as vibrations and impacts, that are considerable and transitory, applied to the carrying structure, and being propagated through the insulation device to the item of equipment, which may be sensitive to these loads.
In order to make the invention easier to understand, the latter is described below more particularly in the context of certain applications associated with the space sector, and for which the present invention is of particular value for the Applicant.
It is well known that certain actuators, widely used for controlling the attitude of satellites, have one or more rotating elements, the balancing of which, always imperfect in practice, generates vibrations that are propagated through the structure of the satellite. It is the case, for example, with reaction wheels, kinetic wheels, momentum wheels, gyrodynes (also called gyroscopic actuators or CMG in the literature), energy storage wheels, etc.
Other items of equipment on board satellites can also generate such vibrations, such as for example compressor-based coolers.
The vibrations created by these items of equipment can be transmitted to the payloads of the satellites and damage their performance, as is the case, for example, for optical observation instruments that are particularly sensitive to movements of the line of sight that are harmful to the quality of the images obtained.
In order to counter these harmful effects, according to the prior art, the disruptive item of equipment or a set of disruptive items of equipment is mounted on an insulation device consisting of an interface for mounting the item of equipment or set of equipment onto the carrying structure. In addition to this mounting function, the insulation device must attenuate the transmission of the vibrations generated by at least one item of equipment according to a certain frequency template dependent on use. If at least one item of equipment is an actuator in torque or in force, the insulation device must also transmit the effective torques or forces generated by this item of equipment according to a frequency template of transmissibility also specified by the user. Moreover, it is desirable, if not necessary, also that the insulation device attenuates the very high dynamic loads applied to the carrying structure during the launch phase of the satellite, which seems to contradict the function of insulation of the vibrations of at least one item of equipment, these vibrations being several orders of magnitude lower than the dynamic loads on launch.
The insulation device according to the invention must therefore operate:                on the ground, in particular during the performance tests and the qualification tests carried out before the launch of the satellite,        during the launch of the satellite, in particularly difficult vibratory, acoustic and impact environments, and        when the satellite is in orbit, where the performance of insulating very small vibrations must achieve the expected levels.        
Finally, the insulation device according to the invention must also sometimes maintain over time a certain stability of alignment of the item or items of vibrating equipment relative to the carrying structure.
The following numerical values correspond to a typical operating range of a particular embodiment of the device of the invention when it is applied to the insulation of actuators such as reaction wheels or gyrodynes on board satellites:                the weight of an item of vibrating equipment to be insulated: typically from 1 kg to 30 kg;        disruptive forces and torques generated by the vibrating equipment: 1 N to 100 N over a frequency range from 10 Hz to 1000 Hz;        attenuation factor sought in vibrations and impacts: 3 to 50 in the range 10 Hz to 1000 Hz (typically an attenuation in gradient −2 in logarithmic scale in the frequency domain);        factor of overstretch of the insulation device: less than 2;        factor of transmissibility sought: 1±5% in the range 0 to 10 Hz;        stability of alignment over time: able to go typically to 0.05°;        environment at launch: typically 20 to 100 g in the range 10-100 Hz (vibrations) and 1000 g in the range 100-1000 Hz (impacts) (g being the acceleration of the field of gravity of the earth).        
At this point in the descriptive specification, it should be noted that the device proposed by the invention and that is presented below may also be used to insulate not a single item of equipment, but, for example, a set of items of equipments at least one of which is disruptive because it vibrates, all mounted on one and the same equipment-holding table. The insulation device according to the invention may also be used as an interface and be used to insulate a portion of a satellite, for example a service module, from another portion of the satellite, for example a payload. In these two cases, the above numerical values, given as an indication, are not necessarily applicable.
Through WO 2007/077350 from the applicant, multi-axis devices are known for insulating at least one item of vibration-generating equipment on board a carrying structure and which comprises at least three, and typically four insulation modules distributed on the periphery of said item of vibrating equipment or of a support of the latter, and such that each insulation module comprises two rigid parts of which one, called the outer part, is designed to be attached to the carrying structure, and the other, called the inner part, is designed to be attached to said item of vibrating equipment or to its support, said inner and outer parts being connected to one another by at least one elastomer insulation pad, attenuating through its deformation on at least one of its axes in tension, compression or shearing, the transmission of low-amplitude vibrations generated by said item of equipment, each insulation module also comprising a lateral (or radial) flexible abutment, and two longitudinal flexible abutments, active in opposite directions, each flexible abutment being mounted on only one of the inner and outer parts, and having a free end facing the other of said inner and outer parts and without contact with said other part at rest.
In order to clearly specify the terms used in this descriptive specification, the reader is referred to the appended FIGS. 1 to 3 and 6 to 8, in which the directions called “longitudinal” Z, “radial” Y and “tangential” X, associated with each orientation module are represented. These directions X, Y, Z are oriented respectively:                for the longitudinal direction Z: on an axis −ZZ called longitudinal of the item of vibrating equipment, because it is substantially perpendicular to its support and/or to the carrying structure,        for the radial direction Y: on an axis −YY called radial, perpendicular to the longitudinal direction Z and passing through a geometric center or center of symmetry of the item of equipment to be insulated,        for the tangential direction X: on an axis −XX called tangential, perpendicular to the two directions Z and Y.        
The flexible abutments of the insulation modules each comprise at least one elastomer element coming into contact with said other rigid part facing it, in the active position of the flexible abutment, during deformations of sufficient amplitude of the insulation pad or pads so that the elastomer element of the flexible abutment works in compression when the abutment is active.
However, this type of embodiment of elastomer insulators according to WO 2007/077350 has a number of limitations.
On the one hand, when the abutments are not active, that is to say during the nominal operating mode of the insulation device, the stiffness in torsion (that is to say about the longitudinal axis Z) of the whole of the insulation device relies only on the shearing stiffness of the insulation pads which are placed in the longitudinal direction Z, and/or in the radial direction Y. This shearing stiffness of the pads is usually much weaker than the stiffness of the pads in tension/compression, and, in certain cases, it is insufficient to withstand the effective stresses that must be transmitted by the item of equipment in torsion in the longitudinal direction Z.
Another limitation comes from the fact that, in the configurations according to the prior art, the torsion modes are not decoupled well in frequency relative to the tilting modes (in the radial direction Y and tangential direction X).
The problem at the basis of the invention is to propose a device for the multi-axis insulation of at least one item of equipment generating vibrations, on board a carrying structure, such as a satellite, similar to those presented above and which remedies the aforementioned drawbacks of the prior art and is more suitable for the various requirements of practice than the known devices, in particular according to WO 2007/077350 aforementioned.